Heat exchanger



May 23, 1967 D. M. DONALDSON HEAT EXCHANGER 2 Sheets-Sheet 1 OriginalFiled Dec. 20, 1962 May 23, 1967 D. M. DONALDSON HEAT EXCHANGER OriginalFiled Dec.

2 Sheets-Sheet 2 [rm/672.2 07: .Dasmrzdflfimzalalson United StatesPatent 3,321,014 HEAT EXCHANGER Desmond M. Donaldson, Oakville, Ontario,Canada, as-

signor to Borg-Warner Corporation, Chicago, 111., a corporation ofIllinois Original application Dec. 20, 1962, Ser. No. 246,070, nowPatent No. 3,228,367, dated Jan. 11, 1966. Divided and this applicationSept. 17, 1965, Ser. No. 506,140

3 Claims. (Cl. 165-185) The present invention is a divisionalapplication of Ser. No. 246,070, filed Dec. 20, 1962, now Patent No.3,228,- 367, granted Jan. 11, 1966, entitled, Method of Manufacturing aHeat Exchanger.

This invention relates to heat exchangers and methods of theirmanufacture, more particularly to a novel method of forming a finstructure from a continuous strip of thin metal stock and the product ofsuch method.

Heat exchangers of the general type to which the present inventionpertains comprise a plurality of spaced, fluid conducting tubes arrangedgenerally parallel to one another, supply and receiving headers of tanksinterconnected by said tubes, and a plurality of heat exchange promotingfins in heat conducting relation with said tubes. This type of heatexchanger has particular utility used as an automobile radiator;although it should be understood that the present invention is notnecessarily limited to this application.

Methods of fabricating fin structure from a continuous strip of metalstock are known in the art. One example is illustrated in R. W. Kritzer,US. Patent No. 2,994,123, issued on Aug. 1, 1961, in which an elongatedstrip of metal stock is severed along spaced longitudinal lines,provided with a plurality of tube receiving apertures, and then bent inalternate directions between adjacent tube apertures to provide anintegral, accordion-pleated structure. Another such example is disclosedin H. E. Schank etaL, US. Patent No. 2,252,209, issued Aug. 12, 1941, in

which asirnilar structure is provided by bending a length of metal stockinto a pleated pattern and inserting heat exchange tubes between thepleated fins. The heat exchange elements disclosed'in Kritzer and Schanket al. are designed to receive the major portion of the cooling (orheating) air flow in a direction parallel to the fold lines.

Briefly described, this invention provides a self-stacking heatexchanger fin structure providing a plurality of elongated substantiallyparallel fin surfaces suitable to receive the major portion of the flowof heat exchange media in a direction across the width dimension of eachindividual fin element. The fins are preferably formed from a continuousstrip of material in a manner such that alternate edges of each fin aretied to the adjacent fin. The tie element provides a means for spacingand aligning the respective fins. Preferably, the tie elements arelocated inwardly from the edge of the respective fins within the body ofthe fin assembly and the ties are preferably in staggered or non-alignedpositions. The ties are preferably twisted subsequent to insertion ofthe tubes to provide a means for diverting the flow of air across thefin elements.

Other and more particular objects and advantages will be apparent fromthe following description taken in conjunction with the appendeddrawings, wherein:

FIGURE 1 is a front elevation view disclosing a heat exchangerconstructed in accordance with the principles of the present invention;

FIGURE 2 is a side elevation view taken along the plane of line 2-2 inFIGURE 1;

FIGURE 3 is a partial plan view of a section of metal stock aftercutting and stamping but prior to folding and assembly of the finstructure into the completed heat exchange unit;

FIGURE 4 is a view taken along the line 44 of FIG- URE 3;

FIGURE 5 is a detailed isometric view illustrating a tie element priorto the step of inserting the tubes;

FIGURE 5A is a detailed isometric view illustrating the tie element inits twisted position subsequent to insertion of the tubes; and

FIGURE 6 is a diagrammatic illustration of the fin structure formingprocess.

Referring now to FIGURES 1 and 2, the numerals 1 and 2 respectivelydesignate a fluid supply and receiving headers or tanks adapted toconduct the heat exchange fluid to and from a local device, such as anautomobile engine for example. A plurality of fluid conducting tubes 4,having a relatively elongated cross section, and commonly referred to asflat tubes, interconnect the supply header 1 with the receiving header2. The zone spanned by the tubes is of course a cooling (or heating)zone adapted to receive a current of a fluid heat exchange mediumflowing in the direction of the arrows (FIG. 2).

In order to increase the effective area of heat exchange, a plurality offin elements are provided, said fin elements being in heat conductingrelationship with the tubes 4. The fin structure comprises a pluralityof superposed, spaced fin sections 6 arranged in generally parallel andgenerally horizontal relationship, each fin section being interconnectedat alternate ends to an adjacent fin section by integral ties 8. Theties preferably have a relatively narrow span with respect to theover-all length of the units to reduce the flow resistance of theseelements. It is particularly important that these tie elements arestrategically positioned in non-aligned positions in successive layersof fins. This enhances the efliciency of the heat exchanger andminimizes the effect of thetie elements in restricting the flow of airacross the tin.

Each fin section is provided with a plurality of tube receivingapertures 10 in superposed relationship with one another, each saidreceiving aperture being surrounded by a flange 12, projecting from theplane of the fin sections, to facilitate connection to the fluidconducting tubes 4 by soldering, brazing, or some other suitable method.

Having described the over-all construction of the heat exchanger unit ascontemplated by the present invention, reference is now made to FIGURES3, 4, and 6. As best illustrated in FIGURE 3, a partial plan view of asection of sheet metal stock prior to bending into the configurationshown in FIGURE 1, the sheet metal stock, preferably of copper, aluminumor some other metal having a high coeflicient of thermal conductivityand preferably not more than one-hundredth of an inch in thickness, issubjected to a series of mechanical operations which need not beperformed in the order described. First of all, the stock is cut to forma plurality of longitudinally spaced groups of slits 14, 15, 16, and 17each group of slits comprising a series of laterally spaced, co-aligned,individual slits extending transversely across said strip to provide aseries of unsevered portions 8 between adjacent individual slits. Next,the stock is provided with a plurality of rela tively short,longitudinally extending slits 18 intersecting each individualtransverse slit adjacent the terminal portions thereof. The tubeapertures 10 are then formed, preferably in a staggered configuration,at locations between adjacent groups of transverse slits. In addition,it has been found to be useful to form the tube engaging flanges 12 inadjacent sections sothat they extend in opposite directions, alternatingthroughout the length of the strip. (FIG. 4.) In so doing, it isapparent from an inspection of FIGURE 4 that this provides a unit inWhich all of the flanges extend either upwardly or downwardly from theplane of the fin sections after the strip is folded into the completedconfiguration as shown in FIGURE 1.

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FIGURE 6 illustrates in diagrammatic form a practical manufacturingprocess for the production of the fin structure previously described.From a storage roll 20, the relatively thin sheet material is deliveredby any known intermittent feed device to a pair of cutting mechanisms 21and 22. These may either be running knife blades or a transverselydirected blade which strikes downwardly on the strip of sheet material.Cutting means 21 is adapted .to form the first of a series oftransversely spaced slits; and the second cutting mechanism 22 forms aspaced series of slits which are staggered with respect to the firstseries, as shown in FIGURE 3. This arrangement results in having theties 8 staggered with respect to each other to minimize excessive airflow resistance due to the span of these ties and balance the heat loadacross the entire surface of the heat exchange-r with respect to eachindividual tube. From the cutting mechanisms the strip is delivered to adie press 24 which simultaneously forms the tube receiving apertures 10in a pair of adjacent fin sections. In order to accomplish this result,one-half of the die forms the strip with flanges extending in onedirection and the other half of the die forms the apertures with flangesextending in the opposite direction. The strip, now in the formillustrated in FIGURE 3, is delivered to a shaping die 26 having matingsections 26a, 26b which corrugate the strip in the form shown betweenthe shaping die and the condensing rollers 28. The condensing rollersengage the opposite edges of the strip to gather each section and bringadjacent fin sections into parallel alignment with all of the tubeapertures coaxially aligned with respect to one another.

The fin stock in its gathered form, is placed in a jig to support thestock during the tube pushing operation. The tubes are pushed throughthe aligned tube apertures in the conventional manner. Subsequent toinsertion of the tube members in the fin stock, the tie elements arepreferably twisted (FIGURE A) to provide a predetermined flow patternacross the fin stock and minimize the resistance to flow of air acrossthe fin stock.

Manifestly, the construction as shown and described is capable of someadditional modification and such modification as may be construed tofall within the scope and meaning of the appended claims is alsoconsidered to be within the spirit and intent of the invention.

I claim:

1. An integral fin structure comprising a plurality of spaced, parallelfin sections in superposed relation joined at alternately opposite edgesby tie elements struck from the edges of said fin sections, each tieelement being par ticularly characterized as having opposite endportions integral with their respective fin sections said tie elementsextending generally perpendicular to each said fin section and spacingthe edges of said fin sections at substantially the same distance as thedistance between the intermediate portions of said fin sections, saidtie elements being further characterized as being staggered with respectto each other whereby the heat load across said structure issubstantially balanced.

2. An integral fin structure comprising a plurality of spaced, parallelfin sections in superposed relation joined at alternately opposite edgesby tie elements struck from the edges of said fin sections, said tieelements beingintegral with at least two fin sections and extendinggenerally perpendicular to each said fin section and having a midportion twisted with respect to its end portions spacing the edges ofsaid fin sections at substantially the same distance as the distancebetween the intermediate portions of said fin sections, said tieelements being further characterized as being staggered with respect toeach other whereby the heat load across said structure is substantiallybalanced.

3. An integral fin structure comprising a plurality of spaced, parallelfin sections in superposed relation joined at alternately opposite edgesby tie elements struck from the edges of said fin sections, said tieelements having opposed ends, each' of which is integral with acorresponding fin section extending generally perpendicular to each saidfin section and having a mid portion twisted with respect to its endportions spacing the edges of said fin sections at substantially thesame distance as the distance between the intermediate portions of saidfin sections.

References Cited by the Examiner UNITED STATES PATENTS 9/1947 Cook l822,430,631 I i/1947 Eskra l6 51 82 ROBERT A. OLEARY, Primary Examiner,CHARLES SUKALO, Examiner.

1. AN INTEGRAL FIN STRUCTURE COMPRISING A PLURALITY OF SPACED, PARALLELFIN SECTIONS IN SUPERPOSED RELATION JOINED AT ALTERNATELY OPPOSITE EDGESBY TIE ELEMENTS STRUCK FROM THE EDGES OF SAID FIN SECTIONS, EACH TIEELEMENT BEING PARTICULARLY CHARACTERIZED AS HAVING OPPOSITE END PORTIONSINTEGRAL WITH THEIR RESPECTIVE FIN SECTIONS SAID TIE ELEMENTS EXTENDINGGENERALLY PERPENDICULAR TO EACH SAID FIN SECTION AND SPACING THE EDGESOF SAID FIN SECTIONS AT SUBSTANTIALLY THE SAME DISTANCE AS THE DISTANCEBETWEEN THE INTERMEDIATE PORTIONS OF SAID FIN SECTIONS, SAID TIEELEMENTS BEING FURTHER CHARACTERIZED AS BEING STAGGERED WITH RESPECT TOEACH OTHER WHEREBY THE HEAT LOAD ACROSS SAID STRUCTURE IS SUBSTANTIALLYBALANCED.